Extra-tropical cyclones that develop near the east coast of Australia often have severe consequences such as flash flooding and damaging winds and seas, as well as beneficial consequences such as being responsible for heavy rainfall events that contribute significantly to total rainfall and runoff. There is subjective evidence that the development of most major events, commonly known as East Coast Lows, is associated with the movement of a high amplitude upper-tropospheric trough system over eastern Australia. This report examines a number of large-scale diagnostic quantities in the upper troposphere associated with east-coast cyclogenesis, based on the ECMWF interim reanalyses. Climatologies of these diagnostic quantities are examined and compared with a database of observed East Coast Low events in order to test this hypothesis. With a view to future impact-based studies, the diagnostics are also compared with severe weather events such as extreme rainfall and wind speeds. Diagnostic quantities based on geostrophic vorticity and isentropic potential vorticity are shown to provide a good indication of the likely occurrence of east-coast cyclogenesis, as well as associated impacts such as extreme rainfall events. Results are examined in relation to seasonal and geographic variations. The potential application of these diagnostics to global climate model simulations of past and future climates is also discussed.
Collection(s) and Series: CAWCR technical report- No. 37
Format: Digital (Free), Hard copy (ill., charts, maps)
ISBN (or other code): 978-1-921826-35-1